I am selling a Fostech Bumpski AK Bump Fire Stock. This stock is in less than perfect condition because I filed the adapter bar down to fit my RPK (which has a thicker receiver than a standard AK). It is still entirely functional, though it might be loose on a standard AK (but once bolted down, I don't see how it would be an issue). It comes with all the nuts and screws that it originally came with. I'm asking $150 for it.

Also something to add, if you're concerned about the adapter bar being filed down, you can order a new one from Fostech for $150 (a new Bumpski costs $450). But again, it's only filed down 1/2 mm on each side, it shouldn't be a problem on a regular AK.